Note: Descriptions are shown in the official language in which they were submitted.
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1 This invention relates to a current supply
system for supplying respective predetermined cur-
rents to terminal devices connected through lines
to a communication equipment.
With a conventional cross-bar exchange,
since the application of a speech current to a
telephone set was effected by means of a trunk cir-
cuit which was operatively connected to the line every
time that a call occurs, it was necessary to use a
circuit and voltage so selected as to match a maximum
line impedance between the exchange and telephone
set. An exchange of either space division or time
division type incorporated with semiconductor elements
which have recently been placed into practical use
also encounters difficulties for passing a large
current through speech path switch elements of the
exchange, so that it is general to supply a speech
current by way of a line circu t associated with
individual telephone sets. In the latter case, with
a single power source, there also arises a need for
matching with a telephone set associated with a
ma~imum line impedance. However, if the line circuit
brought into matching with the telephone set associ-
ated with maximum line impedance is connected to a
low impedance line, increase in power consumption
in the line or increase in heat generation in line
relays results. Thus, where a concentrated incor-
poration of line circuits or rich ir.corporation
thereof on a printèd circuit board is intended to
miniaturize the exchange, the increase in the heat
1 generation has an adverse influence upon other circuits
of the exchange on account of limited incorporation
concentration, degradation of characteristics due to
temperature rise in relays per se, or ambient tempera-
ture rise.
An object of the invention is to provide
a current supply system capable of improving the
incorporation concentration for circuits and reliev-
Ing the temperature-proof characteristics of elemental
parts to be used by reducing power consumption and
heat generation in the current supply circuit there-
by to suppress temperature rise.
~ he invention is characterized in that line
circuits are grouped in accordance with a line
impedance between an exchange and respective tele-
phone sets, and that a voltage is applied to respec-
tive groups of line circuits which corresponds to a
current matching the line impedance for respective
groups of line circuits.
More ~articularly, there is provided a
current supply system for subscriber line circuits
comprising a plurality of line circuits each connected to a
fieparate terminal device through a separated line, said line
circuits divided into a plurality of line circuit groups in
accordance with a line impedance connected to the line circuit,
a separate power source associated with each respective line
circuit group, and means for connecting each line circuit
to a power source which is common to a group of line circuits,
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Other objects and features of the inven-
tion will fully be understood taken in conjunction
with the accompanying drawing in which, a single
figure shows a circuit diagram of current supply
system embodying the invention.
In the single figure, numerical symbols
201, ... , and 201n, on one hand, designate tele-
phone sets each connected to separate primary wind-
ings Ia and Ib of respective transformers 205, ......
and 205n in line circuits 200, ....... , and 200n through
respective low impedance lines 202, .. ...., and 202n
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1 of, for exa~ple, relatively short length, and nwrlcri-
cal syrnbols 301, .... , and 301n, on the other hand,
designate telephone sets each connected to separate
primary windings Ia and Ib of respective transformers
5 305, ..... , and 305n in line circuits 300,
and 300 n through respective high impedance lines
302, ..... , and 302n of, for example, relatively
long length. The two separate primary windings Ia
and Ib of respective transformers 205, ..... , and 205n
are connected with each other through respective
capacitors 204, ..... , and 204n. Similarly, the
two separate primary windings Ia and Ib of respective
transformers 305, ... .., and 305n are connected with
each other through respective capacitors 304, ......
and 304n. While one winding Ia of the primary winding
of respective transformers 205, ..... , and 205n is
connected to respective relay terminals 206, .....
and 206n through one coil of respective line relays
203, ..... , and 203n, the other winding Ib is grounded
through the other coil of the line relays 203, ......
and 203n. Similarly, one primary winding Ia of respec-
tive transformers 305, ..... , and 305n is connected
to respective relay terminals 306, ........ , and 306n
through one coil of respective line relays 303, ......
303n, and other primary winding Ib is grounded throughthe other coil of respective line relays 303, ......
and 303n.
Secondary winding II of respective trans-
formers 205, ..... , and 205n and 305, ..... ..., and 305n
is connected to a switching networ~ 100. The switching
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1 network 100 may be realized in terms of either known
space division type or time division type. A detailed
description of the switching network, however, will
not be given herein because it has no direct relation
5 to the subject of the invention.
The relay terminals 206, ..... , and 206n
respectively associated with the telephone sets 201,
..... , and 201n each connected to the low impedance
lines 202, ...... , and 202n are connected in common
to a power supply terminal 207 connected to one pole
of a power source 208 of a low voltage Vl. The relay
terminals 306, .. ...., and 306n respsctively associated
with the telephone sets 301, ..... , and 301n each
connected to the high impedance lines 302, ......
and 302n are connected in common to a power supply
terminal 307 connected to one pole of a power source
308 of a high voltage V2. The voltages Vl and V2
are determined in accordance with a line impedance
such that currents caused to flow through lines
20 associated with telephone sets 201, ...... , or 201n
and 301, ..... , or 301n when these telephone sets are
hooked off take substantially the same optimum values.
For example, when the telephone set 201 is
hooked off, a speech current is supplied to the tele-
phone set 201 through ground, power source 208, powersupply terminal 207, relay terminal 206, line relay
203, primary winding Ia of transformer 205, line 202,
telephone set 201, line 202, coil of line relay 203
associated with primary winding Ib of tran~former
205, and ground. The speech current continues to
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1 flow while the telephone set 201 i9 hooked off. An
alternating signal such as voice current from the
telephone set 201 flows through the primary winding
Ia of transformer 205, capacitor 204 and primary wind-
ing Ib thereby to interfere with the secondary windingII of transformer 205 at which a corresponding alter-
nating signal is induced which in turn is transmitted
to the switching network 100. Conversely, a voice
current from the switching network 100 counterflows
through the above path to the telephone set 201.
A similar operation holds true for other
telephone sets 201n and 301, ..... , and 301n when they
are hooked off.
As will be understood from the foregoing
description, according to the invention, line cir-
cuits associated with an exchange are grouped (into
two groups in the foregoing embodiment) in accordance
with a line impedance connected to the respective
line circuits, and respective group of line circuits
is connected to a power source of a voltage deter-
mined in accordance with the line impedance, whereby
a current matching the line impedance is supplied to
re~pective terminal devices such as telephone sets.
Where the line circuits are concentratedly incorporat-
ed on a printed circuit board as in present-day ele-
ctronic exchanges, the number of power source wirings
for replaceable unit~ can be reduced.by grouping a
plurality of circuits on the ~ingle printed circuit
board and preferentially connecting in common the
plurality of circuits in the same group to a power
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1 source exclusively used therefor by means of printing
circuit technique. Further, where the distribution
of the line impedances is known in advance, the wiring
for the speech current supply sources can be preformed
simultaneously with production of the replaceable
units.
While, in the foregoing, one embodiment of
the invention has been described, it is noted that
the invention is not limited to such line circuit
arrangement, line impedance distribution, variety
of terminal devices, value of speech current and the
number of line circuit groups as shown in the single
figure.
It should also be noted from the foregoing
description that, according to the invention, since
not only a load on the speech current supply source
but also power consumption in the speech current
supply circuit can be reduced, reduction in the heat
generation and suppression of temperature rise are ;
realized, thereby assuring increase in incorporation
concentration and relief of temperature-proof
characteristic~ of component parts to be used.
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